NC cobalt exhaust install

Good afternoon everyone,
Does anyone have any experience fitting the above exhaust.

I’m currently doing it now on my drive.

I’ve got the exhaust mounted on the hangers no problem, I just need to bolt it up.

My question is regarding the supplied gasket, it’s just like a soft ring that doesn’t sit over the mid pip, it sits on it where the two faces meet.

The new exhaust isn’t flush where the two facedMs meet, there’s about a half inch gap which makes the bolts too short to fit the nuts on the ends.

Is there something obvious I’m doing wrong?



I’ve got mine off ATM, it’s a Cobalt.
I’ve ordered a crush gasket from Mx5parts for when I replace it. My particular back box was supplied with a flat gasket with two bolt holes it takes the shape of the midpipe flange. It didn’t find it sealed very well without a liberal amount of sealant.
Hope the crush gasket fits I’ve ordered.
Wonder if they supplied the correct one for yours. I noted upon removal the front rubber hangers slightly differ to rear ones, front meaning the ones nearest the diff. Wonder if it makes any difference to how the box sits ref mating surfaces?

I’ve pushed the gasket on the mid pipe and like you said it does squash down, but the supplied bolts aren’t long enough.

I’ve used the old bolts for now and once I lined it all up and nipped it, it’s appears to have sealed.

I’m going to get some new bolts from a hardware store and I’ll apply some sort of sealant when I fit them. Any products you can recommend?

There was a gap like that there with the standard back box but minus the gasket.

Personally I’d have though the two faces should be flush but I’ve got nothing to compare it too

Something doesn’t look quite right to my untrained eye. Looks like the flange on the mid pipe is sitting back. As I recall on mine it was flush with the end of the pipe. The bolts supplied with the cobalt back box were certainly long enough

The mid pipe has a bit that sticks out the end, but it doesn’t slot into the back box as it’s too wide. As I said it looked the same with the old back box and there wasn’t even a gasket fitted.

I’ve had to put the gasket on the mid pipe then offer up the back box. But I agree it doesn’t seem right to me.

Here’s how mine looks.

That’s what I was expecting myself. The two faces won’t fit though due to the mid pipe.

I attempted the DIY route to save some money but I might end up taking to an exhaust fitter.

Like I said the original one looked the same aswhoever fitted the mid pipe (as it’s doesn’t look that old) left it that way before

I’ve zoomed in on that picture, it does look a rather large spigot protruding.
Daft question, is the other crush gasket still stuck on the spigot? Sometimes they can really weld themselves on.

It also looks like the ID of the mid pipe flange is larger than the OD of the mid pipe. Could the mid pipe flange have been loose and it somehow got stuck in place? Would a tap with a mallet help?

Not a very good picture, I could have got a better one earlier when I had the car outside.
The picture of my spigot, it’s still got the flat gasket stuck on there.

Mine didn’t look like that when I removed the old back box.

I wire brushed it to clean it up but it looked like one solid piece. I’ll post a pic of the type of gasket it included.

I’ll loosed the bolts tomorrow and give it a few taps with a mallet to see if there is any movement. I’m still unsure why the previous fitter left it that way too.

I might be off base here but it looks like the flange on the midsection is stuck where it is because of the rust. It should move freely to the edge of the pipe thereby allowing it to mate properly to the back box.
I would do a bit of work (grind the rust off) on it to make it meet properly. Otherwise it is not going to seal properly unless you start smearing loads of sealant over it (recipe for disaster)
That’s just what I would do.

All good advice guys, much appreciated. I’ll take it off tomorrow and start again

Something wrong there. Mine fitted like a glove with the supplied gasket, (The first time).
I had a replacement warranty exhaust as a strut broke.
Again, fitted like a glove (same as dosthilldave) and also used some exhaust gasket sealant with it the second time.
From memory, the mid section pipe fitted inside the cobalt and aligned everything up.
Or the other way around.
Also make sure the 4 exhaust rubber hangers are in the correct locations. As 2 are different from the other 2. (See MX5 parts and it shows a picture of which ones go where).
Not sure how old the car is and wondering whether you have had a replacement centre section at some point?. As that “Could” be your answer…
Cheers and hope you get it sorted.

Mine is same as Micks. Fixed flange. Maybe your mid pipe is aftermarket? I’m sure that should be a freely moving flange.

It’s an 07 plate and yes the centre section does look new, obviously wasn’t fitted correctly either. As soon as I undid the bolts it popped open

Checked my recent Cobalt install on my 07 and both surfaces butt up together.